Nutrition Performance - The Ultimate Amino Acid Formula for Post-Workout Recovery Drinks
Today, we have four ways to get amino acids into the bloodstream: 1) whole food protein; 2) intact protein supplements; 3) free form amino acids; and 4) protein hydrolysates.1 Protein can be hydrolyzed (broken into smaller pieces) by enzymes, producing small chains of amino acids called peptides. This process mimics our own digestive actions, thus making it an ideal way to process protein.
Several studies have shown that protein hydrolysates are absorbed more rapidly than free-form amino acids and much more rapidly than intact protein supplements or whole foods.1 This is a desirable trait for serious gym rats who wish to maximize amino acid delivery to the muscle immediately after exercise.
However, whether this apparent advantage over ingestion of intact protein supplement or whole foods has a practical effect of faster muscle mass accretion or improved recovery from exercise has not been adequately studied in exercising individuals.1 Nevertheless, there is recent evidence that protein hydrolysate ingestion has strong insulinotropic effect.
Basic Facts About Insulin
Insulin is peptide hormone produced by the beta cells of the pancreas. The physiological effects of insulin are far-reaching and complex. They are conveniently divided into rapid, intermediate and delayed actions, as listed in Table 1. The best known is the hypoglycemic effect, but there are additional effects on amino acid and electrolyte transport, many enzymes and growth. The net effect of the hormone is storage of carbohydrate, protein and fat.
From our understanding of insulin physiology, we can see different ways in which insulin might be a performance-enhancing agent:
1. By facilitating glucose entry into cells in amounts greater than needed for cellular respiration, it will stimulate glycogen formation. Thus, hyperinsulinemic clamps will both increase muscle glycogen concentrations
prior to events and in the recovery phase after events. Since performance in many events is known to be a function of muscle glycogen stores, “bulking up” these stores will most probably enhance performance.
2. By use of similar hyperinsulinemic clamps post-exercise, it’s likely recovery will be improved.
3. Insulin is also being used in a more haphazard way, particularly to increase muscle mass in bodybuilders. It has been long known that insulin-treated patients with diabetes have an increase in lean body mass when compared with matched controls.
Insulin also transports electrolytes and fluid into muscle cells, which makes them swell and gives the muscle a better definition. Further, a benefit of insulin abuse by competing athletes is that it is undetectable by currently available tests.8 However, abuse of insulin is extremely risky business, as evident in a bodybuilder who developed severe and permanent brain damage after inducing hypoglycemia from using intravenous insulin.2
Protein Hydrolysates, Amino Acids and Insulin Secretion
Formerly, it was believed insulin secretion was controlled almost entirely by the blood glucose concentration. However, as more has been learned about the metabolic functions of insulin for protein and lipid metabolism, it has become apparent that blood amino acids and other factors also play important roles in controlling insulin secretion.
Protein meals, infusion of physiological amino acid mixtures or certain individual amino acids cause insulin release in humans even under conditions in which the blood sugar changes little from its basal level.5 However, changes of blood sugar levels markedly influence the responsiveness of beta cells to individual amino acids. For example, hypoglycemia reduces insulin release to amino acid mixtures and most individual amino acids.
Studies on isolated perfused rat pancreas and islets have demonstrated that physiological amino acid mixtures, and even pharmacological concentrations of individual amino acids, require the presence of permissive levels of glucose to be effective beta cell stimulants. However, leucine is an exception.5 In a recent study by Dr. van Loon et al. and co-workers,6 a total of 10 drinks were tested in eight non-obese males after an overnight fast to investigate the insulinotropic potential of several free amino acids, protein hydrolysates and an intact protein. At zero, 30, 60 and 90 minutes, the subjects received a beverage volume of 3.5 milliliters per kilogram body weight (mL/kg) to ensure a given dose of 0.8 grams carbohydrate per kilogram (g/kg; 50 percent as glucose and 50 percent as maltodextrin) and 0.4 g/kg of an amino acid and protein hydrolysate mixture every hour.
To compare the insulinotropic effect of the ingestion of the protein hydrolysates with that of an intact protein, sodium caseinate was provided in one of the drinks. This resulted in an insulin response that was not significantly different from that found with the control trial (30 percent greater) and tended to be less than the responses observed after ingestion of the protein hydrolysates. Also, after ingestion of the intact protein, plasma amino acid responses over this two-hour
period were in general lower than the responses observed after ingestion of the protein hydrolysates.
Regression analysis of the insulin responses and the changes in the plasma amino acid concentrations over the two-hour period showed a strong positive correlation between the observed insulin response and changes in plasma leucine, phenylalanine and tyrosine concentrations. (However, the correlation observed with tyrosine concentrations may be explained by the fact that tyrosine is formed by the hydroxylation of phenylalanine when large amounts of phenyalanine are ingested).
Interestingly, the addition of free glutamine hardly influenced plasma glutamine levels. Further, the data in this study show clearly that oral ingestion of large amounts of free arginine is not an effective means of increasing plasma insulin concentrations and plasma arginine concentrations. The main conclusion is that oral intake of protein hydrolysates and amino acids in combination with carbohydrates can result in an insulinotropic effect as much as 100 percent greater than with the intake of carbohydrates only.
More Proof of Efficacy
In another excellent study by Dr. van Loon and colleagues,7 after an overnight fast, eight male cyclists visited a laboratory on five occasions, during which a control and two different beverage compositions in two different doses were tested. After they performed a glycogen-depletion protocol, subjects received a beverage (3.5 mL/kg) every 30 minutes to ensure an intake of 1.2 g/kg/hour carbohydrate and zero, 0.2 or 0.4 g/kg/hour protein hydrolysate and amino acid mixture.
After the insulin response was expressed as the area under the curve, only the ingestion of the beverages containing protein hydrolysate, leucine and phenylalanine resulted in a marked increase in insulin response compared with the carbohydrate-only trial. A dose-related effect existed because doubling the dose (0.2-0.4 g/kg/hour) led to an additional rise in insulin response. Plasma leucine, phenylalanine and tyrosine concentrations showed strong correlations with the insulin response.
Plasma amino acid concentrations were generally lower after the ingestion of protein hydrolysate phenylalanine leucine compared to the control drinks, although in the latter, a considerable amount of protein and amino acids were ingested. This seems to suggest that tissue amino acid uptake and possibly also post-exercise net muscle protein balance were increased after the ingestion of this insulinotropic mixture.
This would be in line with several studies demonstrating that an increase in plasma insulin concentration during conditions of hyperaminoacidemia further increases net muscle protein balance in humans. Such a stimulating effect on net protein balance may, in part, also be a consequence of a stimulating effect of leucine on skeletal muscle protein synthesis, independent of an increase in insulin levels.
According to the authors, “This study provided a practical tool to markedly elevate insulin levels and plasma amino acid availability through dietary manipulation, which may be of great value in clinical nutrition, (recovery) sports drinks and metabolic research.” However, the potential of insulintropic protein
hydrolysate and amino acid mixtures to stimulate post-exercise net muscle protein anabolism, and the mechanisms involved, remains to be investigated.
